JP2019536297A - Solid-state optical amplifier with active core and doped cladding in a single chip - Google Patents

Abstract

A fixed optical amplifier is disclosed. The fixed optical amplifier has an active core and a doped clad in one chip. The active optical core passes through a doped cladding in a structure formed on the substrate. Light emitting structures such as LEDs are formed within the optical core and / or adjacent to the optical core. The cladding is doped, for example, with erbium or other rare earth elements or metals. Several exemplary devices and methods of formation are provided. [Selection diagram] FIG.

Description

  The following relates generally to optical components used in optical communication networks, and more particularly to optical devices capable of amplifying optical signals.

  Erbium-doped fiber amplifiers (EDFAs) or praseodymium-doped fiber amplifiers (PDFAs) are widely used in optical networks with 1550 nm or 1310 nm wavelength windows, respectively. FIG. 1 shows a plurality of optical components typically included in prior art EDFAs or PDFAs. The optical power from the pump laser light source 102 is combined with the input signal 101 by a wavelength division multiplexing (WDM) coupler 104. The combined input signal and pump laser light then pass through the portion of fiber 103 whose core is doped with erbium or praseodymium ions. The pump laser light excites erbium or praseodymium ions embedded in the erbium-doped (or praseodymium-doped) fiber 103 to a higher energy level. The optical input signal 101 then induces stimulated emission and is amplified to produce an output signal. However, amplified spontaneous emission (ASE) noise also occurs at the same time, and noise is generated in the amplified input signal 101. Therefore, the output signal 106 includes an amplified input signal and an ASE noise component. An isolator 105 is positioned after the erbium-doped or praseodymium-doped fiber 103. This isolator 105 is intended to prevent backscatter power from downstream optical fibers and other components from re-entering the EDFA or PDFA. This undesirable backscatter power is otherwise amplified, thereby hindering the normal properties and performance of EDFA (or PDFA). Also shown in FIG. 1 is a pump laser monitoring port 107.

FIG. 2A shows the operating principle of an erbium-doped fiber amplifier (EDFA). The figure shows the three energy levels labeled Er ³⁺ ions in silica glass labeled E ₀ , E ₁ , E ₂ . Each energy level is passed through a Stark splitting process, as described, for example, in “Erbium-Doped Fiber Amplifiers, Fundamentals and Technology”, Chapters 8 and 9, PC Becker, NA Olsson and JR Simpson, Academic Press, 1999. Are divided into a plurality of levels or bands. The difference between any two of the energy levels is labeled with the photon wavelength (or wavelength range) corresponding to that energy level transition. The upward arrow indicates the wavelength at which the EDFA can be pumped to excite erbium ions to the indicated higher energy level. For example, a 1480 nm pump laser can be used to excite erbium ions from the E ₀ level to the E ₁ level. Its lifetime is very long, on the order of 10 msec, and the inverted distribution between the E ₀ level and the E ₁ level is suitable for stimulated emission. The downward arrows from E ₁ to E ₀ represent the wavelength range of photons emitted by spontaneous and stimulated emission and amplifying the input signal. Since the E ₁ and E ₀ energy levels are divided into bands, a range of wavelengths can be amplified, as shown in FIG. 2 as 1520-1560 nm.

Similarly, it is possible to use a pump laser 980 nm, excites erbium ions from _{E 0} level to _{E 2} levels. Ions that have risen to the E ₂ level transition rapidly to the E ₁ level via a non-radiative spontaneous emission process. The transition of these ions from the E ₁ level to the E ₀ level results in amplification of the input signal in the range of 1520-1560 nm via stimulated emission. For various reasons, pumping at 980 nm is more efficient than pumping at 1480 nm.

Pump sources with wavelengths below 980 nm, including visible light, can also be used. FIG. 2B shows a more complete view of the energy levels of Er ³⁺ ions. The wavelength scale corresponds to the wavelength of light emitted when an Er ³⁺ ion transitions from a given energy level to the ground state. The energy level diagram shows that Er ³⁺ ions can absorb light from about 1500 nm to less than 400 nm. A low wavelength pump source (ie, less than 980 nm) excites erbium ions to a higher energy level than shown in FIG. 2A, but the overall process for amplifying the input signal via stimulated emission is similar. is there. Also, for different wavelength range input signals, different rare earth elements or other materials including various metals can be used with corresponding different pump source requirements. For example, to amplify an input signal in the 1310 nm wavelength range, praseodymium ions have energy level transitions in the appropriate wavelength range. Amplifying the visible light input signal can also be physically performed as long as the pumping wavelength is shorter than the wavelength of the input light and a suitable dopant is used. Broadband sensitizers can also be used as an aid in activating dopant materials. (For details on broadband sensitizers, see, for example, “Broadband Sensitizers For Erbium-Doped Planar Optical Amplifiers: Review”, A. Polman and F. van Veggel, Journal of Optical Society of America B, Vol. 21, Iss. 5, Can be seen in May 2004.)

  More components are incorporated into individual optical modules with the same limited volume to save space and improve the performance of the network control center, as is done with mobile phones. Fiber splicing between separate optical fiber components is cumbersome and occupies space. Therefore, it is highly desirable to integrate multiple optical components into a single package. As shown in FIG. 1, prior art EDFAs and PDFAs typically utilize separate WDM couplers and isolator components to provide a length of doped fiber (typically 10-20) with a limited bend radius. Incorporate the meter length). In addition, the pump laser source must be an external component or integrated into the EDFA housing. Considering this would limit the size (and cost) reduction that can be achieved with typical prior art optical amplifiers based on the use of doped fibers. Semiconductor optical amplifiers (SOA) can offer size advantages, but typically have limited performance due to higher levels of amplified spontaneous emission (ASE) noise and various non-linear behaviors . Thus, multiple components of a doped fiber (or more generally doped waveguide) optical amplifier can be physically combined into as few components or elements as possible without the performance limitations of a semiconductor optical amplifier. It is desirable to be integrated.

  The optical amplifier includes a substrate and an optical core that is formed on the substrate and provides an optical path from the optical input unit to the optical output unit. One or more light emitting structures are formed on the substrate in and / or adjacent to the optical core. One or more cladding layers are formed on the substrate on which the optical core and the light emitting structure are disposed. The one or more cladding layers have a refractive index that is lower than the refractive index of the optical core. Doped with one or more dopant elements or dopant materials. The electrical contact is connected to the light emitting structure. The light emitting structure illuminates at least a portion of the one or more doped cladding layers in response to the applied voltage difference. The dopant element or the dopant material emits light in the first wavelength range when irradiated with light having a shorter wavelength than the wavelength in the first wavelength range by the light emitting structure.

  In another embodiment, the optical amplifier includes a substrate and an optical core formed on the substrate and providing an optical path from the optical input unit to the optical output unit. One or more light emitting structures are formed on the substrate in and / or adjacent to the optical core. The cladding along the optical core and the light emitting structure has a refractive index lower than that of the optical core. The cladding is doped with one or more dopant elements or dopant materials. The electrical contact is connected to the light emitting structure. The light emitting structure illuminates at least a portion of the one or more doped cladding layers in response to the applied voltage difference. The dopant element or the dopant material emits light in the first wavelength range when irradiated with light having a shorter wavelength than the wavelength in the first wavelength range by the light emitting structure.

  A method of forming an optical amplifier includes the steps of growing a light emitting epitaxial layer on a first substrate, a patterned optical core, and a light emitting structure in and / or adjacent to the optical core. And a step of forming. One or more cladding layers are deposited on the patterned optical core. The one or more cladding layers have a refractive index lower than that of the optical core, and the one or more cladding layers are doped with one or more dopant elements or dopant materials. When the dopant element or the dopant material is irradiated with light having a wavelength shorter than the wavelength in the first wavelength range, the dopant element or the dopant material emits light in the first wavelength range. A first set of electrical connections in contact with the light emitting structure is fabricated on one or more cladding layers. A second substrate is formed on the first set of electrical connections. The first substrate is removed from the patterned optical core formed on the first substrate. A second set of electrical connections in contact with the light emitting structure is created on the surface exposed by removing the first substrate.

  A method of forming a further optical amplifier includes growing a light emitting epitaxial layer on a first surface of a substrate, a patterned optical core, and a light emitting structure in and / or adjacent to the optical core. Forming from the light emitting epitaxial layer. The cladding is deposited along the optical core and the light emitting structure. The cladding has a refractive index lower than that of the optical core and is doped with one or more dopant elements or dopant materials. When the dopant element or the dopant material is irradiated with light having a wavelength shorter than the wavelength in the first wavelength range, the dopant element or the dopant material emits light in the first wavelength range. A first set of electrical connections in contact with the light emitting structure is fabricated on the light emitting structure. A second set of electrical connections is made on the second surface of the substrate or through the second surface and in electrical contact with the light emitting structure.

  Various aspects, advantages, features, and embodiments are included in the following description of exemplary examples, which should be construed in conjunction with the accompanying drawings. All patents, patent applications, papers, other publications, documents, and articles referenced herein are hereby incorporated by reference in their entirety for all purposes. In addition, the subject matter of this application shall prevail within the scope of any inconsistencies or inconsistencies in the definition or use of terms between any of the incorporated publications, documents or materials and this application.

Figure 2 shows an erbium doped (or praseodymium doped) fiber amplifier (EDFA or PDFA, respectively) used to amplify an optical signal. The operating principle of an erbium doped fiber amplifier (EDFA) is shown. A more complete view of the energy levels of Er ³⁺ ions is shown. Fig. 4 illustrates a waveguide layout and routing of one embodiment. 3B illustrates an exemplary manufacturing process of an embodiment as shown in FIG. 3A. 3B shows a cross-sectional view of the embodiment shown in FIG. 3A. 3B shows an enlarged view of a portion of the embodiment shown in FIG. 3A. A typical LED epitaxial structure is shown. FIG. 6B shows the energy band of the LED epitaxial structure shown in FIG. 6A. Fig. 4 illustrates another embodiment having light emitting regions scattered around a waveguide. 8 shows a cross-sectional view of the embodiment shown in FIG. FIG. 11B shows a cross-sectional view of an additional embodiment, also shown in FIG. 11A, that incorporates an LED epitaxial structure in the waveguide core. FIG. 10 shows an enlarged view of a portion of the embodiment shown in FIG. 9. FIG. 10 illustrates a top view of the embodiment shown in FIG. 9, depicting waveguide layout and routing, and waveplate inclusion. 11B illustrates an exemplary manufacturing process for an embodiment as shown in FIG. 11A. FIG. 11B shows a detailed view of a waveplate, such as may be used in an embodiment similar to that shown in FIG. 11A, including coupling of light from and to adjacent waveguides. Fig. 4 illustrates the use of a polarization rotator that utilizes an offset two-core structure surrounded by a common cladding. FIG. 6 illustrates another embodiment that utilizes a polarization rotator at the input port to reduce polarization dependent loss. FIG. FIG. 14 is a perspective view of a polarization rotator as used in the embodiment shown in FIG.

  Although the techniques described below physically integrate multiple components of a doped fiber (or more generally doped waveguide) optical amplifier as a single optical amplifier chip, a semiconductor optical amplifier There are no performance limitations.

  FIG. 3A shows a first set of exemplary embodiments having an active core 305 that emits pump light and also serves as a waveguide core for the input signal. The active core is embedded in a cladding doped with a rare earth element or another suitable dopant material. The input signal is transmitted by the input optical fiber 301 and coupled to the edge 303 of the planar waveguide formed by the active core 305 and the surrounding cladding 306. The active core 305 has a light emitting structure such as a light emitting diode (LED) epitaxial structure based on a material such as InGaAsP, InGaAs, or InGaN compound semiconductor material (described below), and its refractive index (approximately 2.1 to 3.8) is generally higher than the refractive index of the cladding 306. (In the following description, reference will be made to LED embodiments for the sake of simplicity, but more generally this can generally be interpreted as a light emitting structure.) Clad 306 is erbium, praseodymium, thulium, ytterbium, neodymium. Or doped with rare earth elements such as combinations thereof. The dopant material may also be a metal or some other material that can emit light at an appropriate wavelength or wavelength range. The total thickness (indicated by T in FIG. 4) of all epitaxial layers within the active core 305 is a few microns. Erbium is used as an example of a doped rare earth element in the following description without losing generality and applicability to other rare earth elements or other dopant materials. More generally, the dopant element or material of the cladding emits light in the first wavelength range when illuminated with light of a wavelength shorter than the wavelength of the first wavelength range by an LED or other light emitting structure. Selected to release. Here, in many general applications, the first wavelength range is 400 nm to 3000 nm. Erbium is used in much of the discussion below as a representative dopant material, but other dopant materials, including but not limited to other rare earth elements and other metals, are also within the scope of the present invention.

  As shown in the example of FIG. 3A, the active core 305 loops clockwise in the planar chip 300 via a significant number of turns, as indicated by arrows 311a-311f. Next, the active core 305 is inverted at 312a. It then proceeds through a series of counterclockwise loops as indicated by arrows 312b to 312d until it reaches the end of tip edge 317 coupled to output optical fiber 328. The total effective length of the active core can be tens of centimeters, or even 10 meters. The refractive index (RI) of the active core 305 is higher (significantly higher or slightly higher) than the refractive index of the cladding 306 (typically a cladding refractive index in the range of about 1.45 to about 2.01). The optical power is confined within the active core 305 because it is either high). The active core 305 has a cross-sectional dimension on the order of 1 micron or submicron for an operating wavelength of 1300-1600 nm. The dimensions of the active core 305 along the optical path of the loop can be varied based on effective optical power confinement requirements and requirements. For example, sharp turns such as 312a require more powerful power confinement. For this reason, the core dimensions must be slightly larger there. As indicated by 311a-311d, more light power is diffused in the straight portion to induce stimulated emission of erbium ions embedded therein (described below) from the active core 305 into the cladding 306. It is desirable. Accordingly, the width of the active cores 401-407 (indicated by W in FIG. 4) should be smaller to sub-microns.

  FIG. 4 shows a cross-sectional view of “cut line” AA in FIG. 3A. The active core (305) loop of FIG. 3A is shown as cross sections 401-407 in FIG. The surrounding cladding 306 of FIG. 3A is indicated by 421, 422 in FIG. One or more thin layers comprised of the active core and cladding (as described below in the description of the manufacturing method) are bonded to the substrate 410. Positive “point contact” electrodes are distributed and deposited on the p-side of the active LED core loop 305, as illustrated by 441, 442, and positive terminals for supplying a positive voltage to the active LED core loop 305. Interconnected with electrode 445. Similarly, negative “point contact” electrodes are distributed and deposited on the n-side of active LED core loop 305 and interconnected to negative terminal electrode 455, as illustrated by 451, 452, and active LED A negative voltage is supplied to the core loop 305.

The cross sections of the active cores 401 to 407 are surrounded by the upper clad 421 and the lower clad 422. The upper cladding 421 and the lower cladding 422 are made of SiO ₂ (RI of about 1.45), silicon-rich SiO _x , SiO _x N _y (about 1.45 to about 2.01) having Si nanocrystals as a broadband sensitizer. Range RI), or composed of a host material (preferably in an amorphous or nanocluster state) such as a polymer doped with erbium ions (or other rare earth ions). Accordingly, the refractive index (RI) of the cladding material can be in the range of about 1.45 to about 2.01. The active cores 401-407 have wavelengths of about 980 nm or 1480 nm, or in the visible and ultraviolet (UV) range, which excites Er ³⁺ ions (or other dopant materials) embedded in a silica (or SiOxNy) host material. The pump light is emitted at a wavelength of. Visible wavelengths and near infrared and UV wavelengths are also feasible as long as Er ³⁺ ions (or other dopant materials) can be pumped to the desired energy level. If the pumping wavelength is much shorter than the signal wavelength, the broadband sensitizer must be embedded (or coexist) in the optically active dopant material in the cladding to enhance the emission of light from the optically active dopant. Can be. (See, for example, “Broadband Sensitizers For Erbium-Doped Planar Optical Amplifiers: Review”, A. Polman and F. van Veggel, Journal of Optical Society of America B, Vol. 21, Iss. 5, May 2004). If other rare earth elements or other dopants are used for amplification of different input signal wavelengths, the pump light wavelength must be compatible with the type of dopant used and the intended input signal wavelength range. Don't be. Furthermore, amplifying the visible light input signal can also be physically performed as long as the pumping wavelength is significantly shorter than that of the input light and appropriate dopants and sensitizers are used in the cladding.

  The active core can be InGaAs (about 3.4 RI), InGaAsP (about 3.6 RI), InGaN and AlInGaN (about 2.1 RI), or others with a direct bandgap for efficient light emission It can be composed of a direct band gap semiconductor material such as a III-V compound semiconductor containing the above semiconductor material. Accordingly, the RI of the cladding material can generally be in the range of about 1.45 to about 2.01. Also, the RI of the active core can generally range from about 2.1 to about 3.8. By appropriate selection of the active core material and cladding material, both high index contrast waveguides (with strong confinement) and low index contrast waveguides (with weak confinement) can be constructed.

The input signal light propagating along the active core loop 305 of FIG. 3A forms a fundamental mode, and its evanescent field penetrates into the cladding 306 to induce stimulated emission of excited Er ³⁺ ions in the cladding. Thus, stimulated emission photons are coupled back into the active core loop 305 and amplify the fundamental mode. Since the photon energy of the signal light is smaller than the band gap energy of the active layer in the LED quantum well (QW) material or the heterojunction LED structure, the absorption loss of the signal light in the active core 305 is negligible. Furthermore, since the dielectric cladding absorbs very little input signal light like the pump light, the optical loss caused by the cladding is very low.

FIG. 5 is an enlarged view of inset 340 of FIG. 3A. The negative electrode 501 is distributed on top of the active core portions 511-515 and is electrically interconnected by conductive traces 504. The clad parts 530 to 535 are alternately arranged in the core array formed by the core parts 511 to 515. In addition, the up arrow shown by the active core part 512 and the down arrow shown by the active core part 513 have illustrated the propagation direction of signal light. In the fundamental mode electric field distribution 521 propagating in the active core portion 512, most of the optical power is confined in the core, but the evanescent electric field 523 penetrates into the clad 532, and excited Er ³⁺ Stimulated emission of ions is induced, thereby increasing the electric field strength. The same applies to the signal light propagating downward in the active core portion 513 (see arrow 518). Since the refractive index of the cladding material is lower than that of the active core, the coupling of amplified spontaneous emission (ASE) noise from erbium ions in the cladding to the fundamental mode is very limited.

6A and 6B show an example of a typical LED epitaxial structure and a corresponding energy band. (In these figures, the position axis corresponds to the downward direction in FIG. 3B or FIG. 4, and the upward axis in FIG. 6A corresponds to the horizontal direction). In FIG. 6A, an etching stop layer 602 having a composition such as InGaP is initially grown on top of a wafer substrate 601 using metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). Next, an N-type compound semiconductor layer 605 is grown, and then a quantum well (QW) or multiple QW layer 607 is grown. Finally, a P-type layer 609 is added on the QW layer 607. Depending on the desired emission wavelength, the composition of the compound material is selected. For light emission near 980 nm, a QW compound material having a composition of (In _x Ga _1-x ) _0.5 As _0.5 is selected, and for light emission at 1480 nm, the composition (In _x Ga _1-x ) _{0. 5} (As _y P _1-y ) _0.5 compounds are selected. For lower wavelength pump light, AlInGaP can be used for 630 nm emission, InGaN can be used for emission in the range of 420 nm to 480 nm, and AlInGaN for emission in the range of 370 nm to 420 nm. Can do. (For more details, see, for example, “Chapter 1 of Diode Lasers and Photonic Integrated Circuits”, L. Coldren, S. Corzine, and M. Mashanovitch, 2nd Edition, Wiley Publishing, 2012, and Chapter 4 of Introduction to Solid-State Lighting. , A. Zukauskas, M. Shur, and R. Gaska, Wiley Publishing, 2002.) FIG. 6B shows the energy band gap corresponding to the epitaxial structure shown in FIG. 6A. Multiple QW LEDs have high quantum efficiency emission in the visible light range of 65% -95%.

An exemplary procedure for a manufacturing process for manufacturing the material structure of the embodiment as shown in FIGS. 3A, 4 and 5 is shown in FIG. 3B.
1. A semiconductor wafer such as GaAs having a lattice constant similar to that of the next epitaxial layer is selected.
2. An etching stop layer having a composition such as InGaP is grown on the wafer by either metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE).
3. The LED epitaxial structure (total thickness about 1 to 4 microns) is then grown by a continuous MOCVD or MBE process. An example of a typical LED structure is shown in FIG. 6A.
4). As shown in FIGS. 3A, 4 and 5, photolithography is used, followed by chemical vapor etching or wet etching to form the spiral active core loop 305.
5. Using either chemical vapor deposition or physical sputtering, an erbium-doped SiO ₂ layer (having a thickness of about 10 microns), shown as one or more lower cladding layers 422 in FIG. 4, is patterned. Deposited on the active core loop.
6). Lithography, etching, and metal deposition procedures are used to create a positive electrode that extends through the lower cladding to contact the p-side of the active core loop. Metal traces are used to interconnect all positive electrodes. Since these metal traces can dissipate optical power, their width should be minimized.
7). A new substrate having a coefficient of thermal expansion close to that of the cladding and active core (preferably a semiconductor wafer) is bonded to the lower cladding, either epoxy or metallurgically. The new substrate may be a conductive or non-conductive material.
8). The original wafer (in this example, GaAs described in Step 1 above) is removed using wet chemical etching until etching stops at the etch stop layer shown in Step 2.
9. Deposit the top or top erbium doped cladding layer (s) 421 using the same process as step 5 (as shown in FIG. 4).
10. Using the same process as in Step 6, create the negative electrodes for the n-side LED active core and their electrical interconnections.
11. The completed wafer is diced into individual optical amplifier chips having dimensions of about 10 mm × 10 mm.
The procedure and enumerated details of FIG. 3B are intended as an exemplary process and are not exhaustive of possible variations. In FIG. 3B (FIG. 11B below), for the sake of illustration, it is referred to as a “step”, but in actual processing, can any of these listed process phases include multiple sub-steps? Or conversely, several “steps” may be combined in a single processing operation, so that “steps” do not limit how the process is actually performed.

  In practice, positive and negative “point contact” electrodes are properly bonded to the narrow active core loop 305 via the cladding layer 306 (shown in FIG. 3A and also shown in more detail in FIGS. 4 and 5). Can be implemented, but can be difficult in some process flows. FIG. 7 shows another set of embodiments that avoid “point contact” electrodes, whose emission region and waveguide core are defined or made from the same LED epitaxial structure made from the wafer. First, the core loop 705 and the pump light emission region (eg, shaded regions 711, 712, 713) are made from a planar LED epitaxial structure. (As indicated by reference numbers 814, 816 in FIG. 8, the unhatched areas are covered here by cladding). Electrode pads 721-728 are made on pump discharge regions 711, 712, 713, respectively, for electrical wire bonding. The interconnect metal, or trace (shown as 751 in the figure) is intended to ensure an effective current spreading over the pump discharge region 711. Next, a cladding doped with erbium is deposited to surround the core loop 705 except for the pump emission regions 711, 712, 713. The emission region may be inserted into the core loop or arbitrarily positioned (eg, emission regions 715, 716) as long as it is close to the cladding region for good coupling of the pump light. Since the pumped photons have energy below the band gap energy of the LED structure in the core 705, the absorption by the core is limited. Thus, the pump photons can traverse the core several times before reaching the cladding region that is located further from the emission region. If some photons are absorbed by the core 705, they are likely to be “recycled” and re-emitted from the core. In order to maximize the extraction of pump light from the pump emission region, the interface between the emission region and the cladding region may be shaped or textured as illustrated by items 770, 771, 772, Alternatively, the structure illustrated by items 770, 771, 772 may be provided.

  8 is a cross-sectional view of FIG. 7 taken along section line BB. Items 831 and 833 show a plurality of core cross sections, and items 814 and 816 are upper erbium-doped clads corresponding to the core portions 831 and 833, which are located above the core portions 831 and 833. The pump discharge areas are indicated by 811, 812, 813 and the corresponding top electrode pads are indicated by 826, 827, 823, respectively. These lower electrode pads are indicated by 836, 837 and 838, respectively. Lower cladding layer 840 is coupled to substrate 810. The pump light emitted from the emission region 811 first enters the cladding layer at a position indicated by 846 to excite erbium ions inside. Next, the unabsorbed photon passes through the next core 836 and reaches the next site such as the cladding layer 847. Pump discharge from the other two discharge regions 812, 813 behaves similarly. To prevent pump light from leaking from the amplifier chip 800, mirrors or reflective coatings 851, 853 may be applied to the outer edges of the emission regions 811, 813, respectively.

  The manufacturing process of the embodiment shown in FIGS. 7 and 8 can be similar to the process described above and shown in FIG. 3B for the embodiments shown in FIGS. 3A, 4 and 5.

  9 and 11A illustrate yet another set of embodiments that may help avoid manufacturing problems associated with the use of “point contact” electrodes. FIG. 11A shows a top view of the optical amplifier chip 1100, and FIG. 9 is a cross-sectional view taken along the section line CC in FIG. 11A. 10 is an enlarged view of the inset 920 of FIG. As shown in FIGS. 4 and 8, T represents the total thickness of the LED epitaxial layer, and W is the width of the active waveguide core. Typically, T is on the order of a few microns and W is about 1 micron. Therefore, T / W (referred to as aspect ratio) is on the order of 1 or slightly larger. However, in the embodiment shown in FIGS. 9, 10, and 11A, T is about 5-10 microns and W is about 1 micron or submicron. The total thickness T (as explained in the description of the manufacturing process below) is within the heterojunction LED structure represented by the N-type epitaxial layer 901 grown from or on the original wafer substrate 900 and 902. It includes a light emitting quantum well or active layer, a P-type layer 903, and corresponding layers in the active cores 931,932. Thus, T is typically an order of magnitude greater than W so that the aspect ratio is on the order of 10. Furthermore, based on the refractive index of a typical LED structure layer, the refractive index of a QW is generally the highest refractive index in the structure, and its refractive index decreases with distance from the QW. Therefore, there is weak light confinement towards the QW layer. With this type of geometric shape and refractive index profile, the active cores 931, 933, and their respective claddings 947, 940, as shown schematically by item 1012 in FIG. It acts like a slab waveguide with a power density distribution of. The power density distribution aligns its peak power point with the QW 1002 with its long axis positioned along the active core slab 1001 (ie, the X axis shown in FIG. 10).

  9 and 10, it should be noted that the N-type epitaxial layer represented by 901 and the lower half of the active cores 931 and 933 are grown or formed on the substrate 900. The substrate material may be conductive or non-conductive. If the substrate 900 is conductive, an electrical connection to the N-type epitaxial layer may be made on the back side of the substrate, as shown in FIG. On the other hand, if the substrate 900 is non-conductive, an etching process (or any other suitable process) is used to penetrate the substrate material to establish an electrical connection to the underside of the N-type epitaxial layer. It is necessary to form vias or through holes.

  The fundamental mode power distribution 1012 is said to produce two dielectric polarizations, referred to as the TE mode (mainly the electric field along the X axis in FIG. 10) and the TM mode (mainly the electric field along the Y axis). Can do. The coupling coefficient of stimulated emission from erbium ions in the cladding layers 947 and 940 into the active cores 931 and 933 is expected to be slightly different between the TE mode and the TM mode. Therefore, the gain of TE mode and TM mode (in optical amplification) is also slightly different. Thus, amplification has polarization dependence, which can be negative for many applications. To improve this, as shown in FIG. 11A, a 180 degree phase shift (also referred to as half-wave shift) wave plate 1108 may be inserted into a slot 1102 added at approximately the midpoint of the core loop 1105. Thus, the signal that is amplified when entering the optical amplifier chip at the input port 1101 and propagating to the output port 1120 has been “exchanged” for half of the amplification loop (ie, from the waveplate 1108 to the output port 1120). Has two polarizations. Its position of the wave plate 1108 along the core loop 1105 can be optimized to minimize the polarization dependence of the optical amplifier chip 1100. In addition, waveplates may be similarly introduced into other embodiments described herein as needed or desired.

  Wave plate 1108 is only a few hundred microns thick, but causes coupling losses between the input and output waveguides, as shown in FIG. 12A, which is an enlarged view of inset 1130 of FIG. 11A. As shown in FIG. 12A, the coupling loss can be reduced by changing the waveguide geometry on either side of the waveplate 1108 (shown as item 1205 in FIG. 12A). In the embodiment shown in FIG. 12A, the wave plate 1205 between the two waveguide core ends 1211 and 1212 is formed by tapering the waveguide core ends 1211 and 1212 of the input waveguide 1221 and the output waveguide 1222, respectively. The sensitivity of the coupling loss to the axial distance of the slot 1202 (denoted by s) is low (eg, “Highly Efficient Coupling Semiconductor Spot-Size Converter with an InP / InAlAs Multiple-Quantum-Well Core”, N. Yoshimoto , et al., Applied Optics, Vol. 34, No. 6, Feb. 1995). The cladding material between the tapered waveguide core ends 1211, 1212 and the wave plate 1205 improves the coupling of light into and out of the wave plate. Other beam expansion methods for waveguide modes (eg, “Arrayed Waveguide Collimator for Integrating Free-Space Optics on Polymer Waveguide Devices”, JS Shin, et al., Optics Express 23801, Vol. 22, No. 20, Oct Is also within the scope of this embodiment before entering the waveplate 1205.

  FIG. 12B shows an example of an embodiment of a polarization rotator that utilizes an offset two-core structure surrounded by a common cladding 1257 (“Silicon Photonic Circuit with Polarization Diversity”, H. Fukuda, et al., Optics Express 4872, Vol. 16, No. 7, March 2008). An input signal having random polarization is sent to the input port 1250 of the first core 1251 and is coupled into two modes denoted TE and TM. Each mode is converted by birefringence as it passes through a second core having a refractive index (RI) that is less than the refractive index (RI) of the first core. When the second core 1256 is appropriately lengthened, the TE mode is converted to TM mode, and the TM mode is converted to TE mode at the output port 1258 of the first core 1251. A polarization rotator such as the prior art embodiment shown in FIG. 12B can be used to replace the waveplate structure shown in FIGS. 11A, 12A.

  FIGS. 13 and 14 illustrate another set of methods utilizing the different methods for managing the polarization dependence of the optical amplifier chip 1100 described above and illustrated in FIG. 11A (and FIGS. 9 and 10). An embodiment is shown. In FIG. 13, the waveplate 1108 of FIG. 11A is removed, and instead a polarization coupler or mixing structure 1308 is added between the input port 1101 and the start of the active core loop 1105 to provide such polarization coupling or mixing. Identical to FIG. 11A, except that the structure can be used as well in other embodiments presented herein as needed or desired. (A top view of the polarization coupler 1308 is shown in FIG. 14. The signal light emitted to the input port 1101 has two polarization modes, a mode such as TE mode (mainly the electric field along the y-axis) and TM. Mode can be broken down into modes (mainly along the x-axis).) Both modes are driven by polarization splitter 1402 in two optical paths 1407 (carrying TM mode), 1408 (carrying TE mode). It propagates along the waveguide part 1401 until it is divided. The TE mode is converted into the TM mode by the polarization rotator 1409 as illustrated in FIG. Thereafter, the two TM modes in the optical paths 1407 and 1408 are respectively coupled by a coupler 1415 and coupled to the beginning of the active core loop 1105. Therefore, only the TM mode propagates and is amplified through the full active core loop 1105. Similarly, polarization combiner 1308 can also be used to convert an input signal having random polarization into a signal that primarily carries a TE mode.

  The embodiment shown in FIGS. 9, 10, and 11A and the similar embodiment shown in FIGS. 13 and 14 are similar to the LED light emitting areas shown in the embodiments of FIGS. More generally, it has a light emitting region. These LED light emitting areas 911, 912, 913 (see FIG. 9) are used to increase pump power, but the active cores 931, 933 themselves emit light (as in the embodiment shown in FIG. 3A). It would be worth mentioning that they can be removed. Accordingly, in the embodiment of FIGS. 9, 10, and 11A (and the embodiments of FIGS. 13 and 14), the positive current spreading metal layer 908 has the active cores 931 and 933 and the LED light emitting regions 911 and 912. 913, which can be deposited directly on the P-type layer of the LED structure. Further, the current spreading layer 908 may be applied on the cladding region. This current spreading layer 908 is relatively distant from the fundamental mode power distribution and therefore does not dissipate much signal power. The negative current spreading metal layer 921 is deposited on the back side of the original wafer substrate 900 when the substrate is a conductive material. The positive connection wire 915 and the negative connection wire 925 are bonded to bonding pads 909 and 924, respectively, and supply voltage and current to the LED structure. If the substrate 900 is a non-conductive material, vias or through holes must be formed through the substrate so that negative electrode connections can be formed in the N-type epitaxial layer as described above.

An exemplary procedure of the manufacturing process for manufacturing the material structure of the embodiment shown in FIGS. 9, 10, and 11A and the similar embodiment shown in FIGS. 13 and 14 is shown in FIG. 11B.
1. A semiconductor wafer such as GaAs having a lattice constant similar to that of the next epitaxial layer is selected.
2. An N-type layer and a QW layer are grown on the wafer by either metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) so as to have the LED structure shown in FIG. Grow.
3. As shown in FIGS. 9, 10, and 11A, using photolithography and then using chemical vapor etching or wet etching, the spiral active core loop 1105 (and LED light emitting region) and its corresponding grooves And a slot 1102 for later insertion of the waveplate.
4). Using either chemical vapor deposition or physical sputtering, an erbium-doped SiO ₂ layer is deposited in the trench until the cladding material is flush with the active core loop N-type layer.
5. A metal layer is deposited so that a positive current is diffused, and then the bond pad is deposited.
6). For negative current spreading, a metal layer is deposited on the back side of the wafer substrate, and then the bond pad (s) are deposited. (As described above, if the wafer substrate is a non-conductive material, vias or through holes are formed through the substrate material to establish electrical connection between the negative bond pad and the N-type epitaxial layer. There must be.)
7). The completed wafer is diced into individual optical amplifier chips having dimensions of about 10 mm × 10 mm, and then a wave plate 1108 is inserted.
Similar to FIG. 3B above, FIG. 11B is intended as an example, and variations and alternatives may be employed, and the use of “steps” in FIG. 11B is for illustrative purposes.

  The top and bottom cladding layers in the embodiments described in FIGS. 3A, 4, 5, 7, and 8 are not the same as those in the embodiments described in FIGS. 9, 10, 11 A, 13, and 14. Note that it is not required. This is because the active core (in the embodiment shown in FIGS. 9, 10, 11A, 13, and 14) and the surrounding cladding act like a slab waveguide. This eliminates the need to remove the original substrate wafer and then bond a new wafer to the LED epitaxial structure.

  The foregoing detailed description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above description. The described embodiments are selected to best explain the principles involved and their practical application, thereby rendering the various embodiments suitable for specific uses contemplated by other persons skilled in the art. , With various changes, to make the best use. It is intended that the scope of the invention be defined by the appended claims.

The foregoing detailed description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above description. The described embodiments are selected to best explain the principles involved and their practical application, thereby rendering the various embodiments suitable for specific uses contemplated by other persons skilled in the art. , With various changes, to make the best use. It is intended that the scope of the invention be defined by the appended claims.
The following items are the elements described in the claims at the time of international application.
(Item 1)
A substrate,
An optical core formed on the substrate and providing an optical path from the light input section to the light output section;
One or more light emitting structures formed on the substrate in and / or adjacent to the optical core;
One or more cladding layers formed on the substrate on which the optical core and the light emitting structure are disposed, having a refractive index lower than the refractive index of the optical core; The one or more cladding layers doped with a dopant material;
An electrical contact connected to the light emitting structure, wherein the light emitting structure irradiates at least a portion of the one or more doped cladding layers in response to a voltage difference applied to the electrical contact. Contacts,
With
The optical element that emits light in the first wavelength range when the dopant element or dopant material is irradiated with light having a wavelength shorter than the wavelength in the first wavelength range by the light emitting structure.
(Item 2)
Item 4. The optical amplifier of item 1, wherein the light emitting structure comprises a light emitting diode (LED) structure.
(Item 3)
Item 3. The optical amplifier of item 2, wherein the LED structure comprises one or more quantum wells.
(Item 4)
The optical amplifier according to item 1, wherein the light emitting structure is formed in at least a part of the optical core.
(Item 5)
The optical amplifier according to item 1, wherein the light emitting structure is formed on the substrate adjacent to at least a portion of the optical core and separated from the optical core by the one or more cladding layers.
(Item 6)
The optical amplifier according to item 1, wherein the first wavelength range is 400 nm to 3000 nm.
(Item 7)
The optical amplifier of item 1, wherein the one or more dopant elements or dopant materials comprise one or more rare earth elements or metals.
(Item 8)
Item 8. The optical amplifier according to Item 7, wherein the one or more rare earth elements include erbium.
(Item 9)
8. The optical amplifier according to item 7, wherein the one or more rare earth elements include one or more elements of praseodymium, thulium, ytterbium, or neodymium.
(Item 10)
Item 2. The optical core according to item 1, wherein when the optical core is formed on the substrate, the optical core has a spiral geometric shape that loops back so that adjacent portions of the optical path extend in opposite directions. Optical amplifier.
(Item 11)
The optical amplifier of item 1, wherein the one or more cladding layers comprise a broadband sensitizer.
(Item 12)
The optical amplifier according to item 1, further comprising a wave plate in the optical path from the optical input unit to the optical output unit.
(Item 13)
The optical amplifier according to item 1, further comprising a polarization rotator in the optical path from the optical input unit to the optical output unit.
(Item 14)
The optical amplifier further includes a polarization coupling structure between the optical input unit and at least a part of the optical core,
The optical amplifier according to item 1, wherein the polarization coupling structure includes a polarization rotator that allows polarization of light incident on the light input unit to be coupled into a single polarization.
(Item 15)
A substrate,
An optical core formed on the substrate and providing an optical path from the light input section to the light output section;
One or more light emitting structures formed on the substrate in and / or adjacent to the optical core;
A clad along the optical core and the light emitting structure, the clad having a refractive index lower than that of the optical core and doped with one or more dopant elements or dopant materials;
An electrical contact connected to the light emitting structure, wherein the light emitting structure irradiates at least a portion of the doped cladding in response to a voltage difference applied to the electrical contact; and
With
The optical element that emits light in the first wavelength range when the dopant element or dopant material is irradiated with light having a wavelength shorter than the wavelength in the first wavelength range by the light emitting structure.
(Item 16)
Item 16. The optical amplifier of item 15, wherein the light emitting structure comprises a light emitting diode (LED) structure.
(Item 17)
Item 17. The optical amplifier of item 16, wherein the LED structure comprises one or more quantum wells.
(Item 18)
16. The optical amplifier according to item 15, wherein the light emitting structure is formed in at least a part of the optical core.
(Item 19)
16. The optical amplifier according to item 15, wherein the light emitting structure is formed on the substrate adjacent to at least a part of the optical core and separated from the optical core by the cladding.
(Item 20)
Item 16. The optical amplifier according to Item 15, wherein the first wavelength range is 400 nm to 3000 nm.
(Item 21)
16. The optical amplifier of item 15, wherein the one or more dopant elements or dopant materials include one or more rare earth elements or metals.
(Item 22)
Item 22. The optical amplifier according to Item 21, wherein the one or more rare earth elements include erbium.
(Item 23)
Item 22. The optical amplifier according to Item 21, wherein the one or more rare earth elements include one or more of praseodymium, thulium, ytterbium, or neodymium.
(Item 24)
16. The optical amplifier according to item 15, further comprising a wave plate in the optical path from the optical input unit to the optical output unit.
(Item 25)
16. The optical amplifier according to item 15, further comprising a polarization rotator in the optical path from the optical input unit to the optical output unit.
(Item 26)
The optical amplifier further includes a polarization coupling structure between the optical input unit and at least a part of the optical core,
Item 16. The optical amplifier according to Item 15, wherein the polarization coupling structure includes a polarization rotator that allows polarization of light incident on the light input unit to be coupled into a single polarization.
(Item 27)
16. The optical amplifier according to item 15, wherein the cladding includes a broadband sensitizer.
(Item 28)
16. The optical core according to item 15, wherein when the optical core is formed on the substrate, the optical core has a spiral geometric shape that loops back so that adjacent portions of the optical path extend in directions opposite to each other. Optical amplifier.
(Item 29)
A method of forming an optical amplifier comprising:
Growing a light emitting epitaxial layer on a first substrate;
Forming a patterned optical core and a light emitting structure in and / or adjacent to the optical core from the light emitting epitaxial layer;
Depositing one or more cladding layers on the patterned optical core, the one or more cladding layers having a refractive index lower than a refractive index of the optical core; The cladding layer is doped with one or more dopant elements or dopant materials, and the dopant elements or dopant materials are irradiated with light having a wavelength shorter than a wavelength in the first wavelength range, Emitting light in a wavelength range, and
Creating a first set of electrical connections in contact with the light emitting structure on the one or more cladding layers;
Forming a second substrate on the first set of electrical connections;
Removing the first substrate from the patterned optical core formed on the first substrate;
Creating a second set of electrical connections in contact with the light emitting structure on a surface exposed by removing the first substrate;
A method of forming an optical amplifier.
(Item 30)
The method further comprises:
Forming one or more additional cladding layers on the surface exposed by removing the first substrate prior to making the second set of electrical connections;
The second set of electrical connections is formed on the one or more additional cladding layers;
The one or more additional cladding layers have a refractive index lower than the refractive index of the optical core;
30. The method of item 29, wherein the one or more additional cladding layers are doped with one or more rare earth elements or other dopant materials.
(Item 31)
The method further comprises:
Forming an etch stop layer on the first substrate before growing the light emitting epitaxial layer;
30. The method of item 29, wherein the light emitting epitaxial layer is grown on the etch stop layer.
(Item 32)
30. The method of item 29, wherein the light emitting structure comprises a light emitting diode (LED) structure.
(Item 33)
33. A method according to item 32, wherein the LED structure comprises one or more quantum wells.
(Item 34)
30. The method of item 29, wherein the light emitting structure is formed in at least a portion of the optical core.
(Item 35)
30. The method of item 29, wherein the light emitting structure is formed on the first substrate adjacent to at least a portion of the optical core and separated from the optical core by the one or more cladding layers.
(Item 36)
30. The method of item 29, wherein the first wavelength range is 400 nm to 3000 nm.
(Item 37)
28. A method according to item 27, wherein the one or more dopant elements or dopant materials include one or more rare earth elements or metals.
(Item 38)
40. The method of item 37, wherein the one or more rare earth elements comprises erbium.
(Item 39)
38. The method of item 37, wherein the one or more rare earth elements comprises one or more of praseodymium, thulium, ytterbium, or neodymium.
(Item 40)
30. The method of item 29, wherein the patterned optical core and the light emitting structure are formed by an etching process.
(Item 41)
30. The method of item 29, wherein the one or more cladding layers are deposited by a chemical vapor deposition process.
(Item 42)
30. The method of item 29, wherein the one or more cladding layers are deposited by a sputtering process.
(Item 43)
A method of forming an optical amplifier comprising:
Growing a light emitting epitaxial layer on a first surface of the substrate;
Forming a patterned optical core and a light emitting structure in and / or adjacent to the optical core from the light emitting epitaxial layer;
Depositing a cladding along the optical core and the light emitting structure, the cladding having a refractive index lower than a refractive index of the optical core, the cladding comprising one or more dopant elements or dopants Doped with a material, and the dopant element or dopant material emits light in the first wavelength range when illuminated with light having a wavelength shorter than a wavelength in the first wavelength range; and
Producing a first set of electrical connections on the light emitting structure in contact with the light emitting structure;
Creating a second set of electrical connections on or through the second surface of the substrate and in electrical contact with the light emitting structure;
A method of forming an optical amplifier comprising:
(Item 44)
The substrate is conductive;
45. The method of item 43, wherein the second set of electrical connections is formed on the second surface of the substrate.
(Item 45)
44. The method of item 43, wherein the second set of electrical connections penetrates the substrate and thereby contacts the light emitting structure.
(Item 46)
44. The method of item 43, wherein the light emitting structure comprises a light emitting diode (LED) structure.
(Item 47)
47. A method according to item 46, wherein the LED structure comprises one or more quantum wells.
(Item 48)
44. The method of item 43, wherein the light emitting structure is formed in at least a portion of the optical core.
(Item 49)
44. The method of item 43, wherein the light emitting structure is formed on a first surface of the substrate adjacent to at least a portion of the optical core and separated from the optical core by the cladding.
(Item 50)
44. A method according to item 43, wherein the first wavelength range is 400 nm to 3000 nm.
(Item 51)
44. The method of item 43, wherein the one or more dopant elements or dopant materials comprise one or more rare earth elements or metals.
(Item 52)
52. The method of item 51, wherein the one or more rare earth elements comprises erbium.
(Item 53)
52. The method of item 51, wherein the one or more rare earth elements include one or more of praseodymium, thulium, ytterbium, or neodymium.
(Item 54)
44. The method of item 43, wherein the patterned optical core and the light emitting structure are formed by an etching process.
(Item 55)
44. The method of item 43, wherein the cladding is deposited by a chemical vapor deposition process.
(Item 56)
44. The method of item 43, wherein the cladding is deposited by a sputtering process.

Claims (56)

A substrate,
An optical core formed on the substrate and providing an optical path from the light input section to the light output section;
One or more light emitting structures formed on the substrate in and / or adjacent to the optical core;
One or more cladding layers formed on the substrate on which the optical core and the light emitting structure are disposed, having a refractive index lower than the refractive index of the optical core; The one or more cladding layers doped with a dopant material;
An electrical contact connected to the light emitting structure, wherein the light emitting structure irradiates at least a portion of the one or more doped cladding layers in response to a voltage difference applied to the electrical contact. Contacts,
With
The optical element that emits light in the first wavelength range when the dopant element or dopant material is irradiated with light having a wavelength shorter than the wavelength in the first wavelength range by the light emitting structure.   The optical amplifier of claim 1, wherein the light emitting structure comprises a light emitting diode (LED) structure.   The optical amplifier of claim 2, wherein the LED structure comprises one or more quantum wells.   The optical amplifier according to claim 1, wherein the light emitting structure is formed in at least a part of the optical core.   The optical amplifier of claim 1, wherein the light emitting structure is formed on the substrate adjacent to at least a portion of the optical core and separated from the optical core by the one or more cladding layers.   The optical amplifier according to claim 1, wherein the first wavelength range is 400 nm to 3000 nm.   The optical amplifier of claim 1, wherein the one or more dopant elements or dopant materials comprise one or more rare earth elements or metals.   The optical amplifier according to claim 7, wherein the one or more rare earth elements include erbium.   The optical amplifier according to claim 7, wherein the one or more rare earth elements include one or more elements of praseodymium, thulium, ytterbium, or neodymium.   2. The optical core according to claim 1, wherein when the optical core is formed on the substrate, the optical core has a spiral geometric shape that loops back so that adjacent portions of the optical path extend in opposite directions. Optical amplifier.   The optical amplifier of claim 1, wherein the one or more cladding layers comprise a broadband sensitizer.   The optical amplifier according to claim 1, further comprising a wave plate in the optical path from the optical input unit to the optical output unit.   The optical amplifier according to claim 1, further comprising a polarization rotator in the optical path from the optical input unit to the optical output unit. The optical amplifier further includes a polarization coupling structure between the optical input unit and at least a part of the optical core,
The optical amplifier according to claim 1, wherein the polarization coupling structure includes a polarization rotator that allows polarization of light incident on the light input unit to be coupled into a single polarization. A substrate,
An optical core formed on the substrate and providing an optical path from the light input section to the light output section;
One or more light emitting structures formed on the substrate in and / or adjacent to the optical core;
A clad along the optical core and the light emitting structure, the clad having a refractive index lower than that of the optical core and doped with one or more dopant elements or dopant materials;
An electrical contact connected to the light emitting structure, the electrical contact irradiating at least a portion of the doped cladding in response to a voltage difference applied to the electrical contact; and
The optical element that emits light in the first wavelength range when the dopant element or dopant material is irradiated with light having a wavelength shorter than the wavelength in the first wavelength range by the light emitting structure.   The optical amplifier of claim 15, wherein the light emitting structure comprises a light emitting diode (LED) structure.   The optical amplifier of claim 16, wherein the LED structure comprises one or more quantum wells.   The optical amplifier according to claim 15, wherein the light emitting structure is formed in at least a part of the optical core.   The optical amplifier according to claim 15, wherein the light emitting structure is formed on the substrate adjacent to at least a part of the optical core and separated from the optical core by the cladding.   The optical amplifier according to claim 15, wherein the first wavelength range is 400 nm to 3000 nm.   The optical amplifier of claim 15, wherein the one or more dopant elements or dopant materials comprise one or more rare earth elements or metals.   The optical amplifier of claim 21, wherein the one or more rare earth elements comprises erbium.   The optical amplifier of claim 21, wherein the one or more rare earth elements include one or more of praseodymium, thulium, ytterbium, or neodymium.   The optical amplifier according to claim 15, further comprising a wave plate in the optical path from the optical input unit to the optical output unit.   The optical amplifier according to claim 15, further comprising a polarization rotator in the optical path from the optical input unit to the optical output unit. The optical amplifier further includes a polarization coupling structure between the optical input unit and at least a part of the optical core,
The optical amplifier according to claim 15, wherein the polarization coupling structure includes a polarization rotator that allows polarization of light incident on the optical input unit to be coupled into a single polarization.   The optical amplifier according to claim 15, wherein the cladding includes a broadband sensitizer.   16. The optical core according to claim 15, wherein when the optical core is formed on the substrate, the optical core has a spiral geometric shape that loops back so that adjacent portions of the optical path extend in opposite directions. Optical amplifier. A method of forming an optical amplifier comprising:
Growing a light emitting epitaxial layer on a first substrate;
Forming a patterned optical core and a light emitting structure in and / or adjacent to the optical core from the light emitting epitaxial layer;
Depositing one or more cladding layers on the patterned optical core, the one or more cladding layers having a refractive index lower than a refractive index of the optical core; The cladding layer is doped with one or more dopant elements or dopant materials, and the dopant elements or dopant materials are irradiated with light having a wavelength shorter than a wavelength in the first wavelength range, Emitting light in a wavelength range, and
Creating a first set of electrical connections in contact with the light emitting structure on the one or more cladding layers;
Forming a second substrate on the first set of electrical connections;
Removing the first substrate from the patterned optical core formed on the first substrate;
Creating a second set of electrical connections in contact with the light emitting structure on a surface exposed by removing the first substrate;
A method of forming an optical amplifier. The method further comprises:
Forming one or more additional cladding layers on the surface exposed by removing the first substrate prior to making the second set of electrical connections;
The second set of electrical connections is formed on the one or more additional cladding layers;
The one or more additional cladding layers have a refractive index lower than the refractive index of the optical core;
30. The method of claim 29, wherein the one or more additional cladding layers are doped with one or more rare earth elements or other dopant materials. The method further comprises:
Forming an etch stop layer on the first substrate before growing the light emitting epitaxial layer;
30. The method of claim 29, wherein the light emitting epitaxial layer is grown on the etch stop layer.   30. The method of claim 29, wherein the light emitting structure comprises a light emitting diode (LED) structure.   34. The method of claim 32, wherein the LED structure comprises one or more quantum wells.   30. The method of claim 29, wherein the light emitting structure is formed in at least a portion of the optical core.   30. The method of claim 29, wherein the light emitting structure is formed on the first substrate adjacent to at least a portion of the optical core and separated from the optical core by the one or more cladding layers. .   30. The method of claim 29, wherein the first wavelength range is 400 nm to 3000 nm.   28. The method of claim 27, wherein the one or more dopant elements or dopant materials comprise one or more rare earth elements or metals.   38. The method of claim 37, wherein the one or more rare earth elements comprises erbium.   38. The method of claim 37, wherein the one or more rare earth elements comprises one or more of praseodymium, thulium, ytterbium, or neodymium.   30. The method of claim 29, wherein the patterned optical core and the light emitting structure are formed by an etching process.   30. The method of claim 29, wherein the one or more cladding layers are deposited by a chemical vapor deposition process.   30. The method of claim 29, wherein the one or more cladding layers are deposited by a sputtering process. A method of forming an optical amplifier comprising:
Growing a light emitting epitaxial layer on a first surface of the substrate;
Forming a patterned optical core and a light emitting structure in and / or adjacent to the optical core from the light emitting epitaxial layer;
Depositing a cladding along the optical core and the light emitting structure, the cladding having a refractive index lower than a refractive index of the optical core, the cladding comprising one or more dopant elements or dopants Doped with a material, and the dopant element or dopant material emits light in the first wavelength range when illuminated with light having a wavelength shorter than a wavelength in the first wavelength range; and
Producing a first set of electrical connections on the light emitting structure in contact with the light emitting structure;
Creating a second set of electrical connections on or through the second surface of the substrate and in electrical contact with the light emitting structure;
A method of forming an optical amplifier comprising: The substrate is conductive;
44. The method of claim 43, wherein the second set of electrical connections is formed on the second surface of the substrate.   44. The method of claim 43, wherein the second set of electrical connections penetrates the substrate and thereby contacts the light emitting structure.   44. The method of claim 43, wherein the light emitting structure comprises a light emitting diode (LED) structure.   48. The method of claim 46, wherein the LED structure comprises one or more quantum wells.   44. The method of claim 43, wherein the light emitting structure is formed in at least a portion of the optical core.   44. The method of claim 43, wherein the light emitting structure is formed on a first surface of the substrate adjacent to at least a portion of the optical core and separated from the optical core by the cladding.   44. The method of claim 43, wherein the first wavelength range is 400 nm to 3000 nm.   44. The method of claim 43, wherein the one or more dopant elements or dopant materials comprise one or more rare earth elements or metals.   52. The method of claim 51, wherein the one or more rare earth elements comprises erbium.   52. The method of claim 51, wherein the one or more rare earth elements comprises one or more of praseodymium, thulium, ytterbium, or neodymium.   44. The method of claim 43, wherein the patterned optical core and the light emitting structure are formed by an etching process.   44. The method of claim 43, wherein the cladding is deposited by a chemical vapor deposition process.   44. The method of claim 43, wherein the cladding is deposited by a sputtering process.

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